While Windows 7 seems to work better than I expected, this is the worst new feature ever imagined. They went to all this trouble to make minimized applications show up as active miniature images on the task bar, but then ones that haven't been used recently go inactive, basically they're pushed out of the cache, and their miniature images are no longer useful and it takes ages to wake the applications up again. Now I want my XP task bar back! Wahhhhh!
So far, I haven't found a solution to this. In fact, there seems to be only one complaint about it on the M$ forums. This one guy, Mike89, back in 2009, put up completely clear explanations of the problem. Nobody responded, or those that did were morons who didn't bother to read what he had written before firing off answers that didn't have anything to do with the problem. Amusingly, he now seems to be banned. Here's the thread:
http://windows7forums.com/windows-7-support/27872-taskbar-explorer-windows-going-blank.html
Oh wait, here's a clue: This makes the taskbar more XP-like!
http://www.techguideforum.com/how-do-i-minimize-windows-on-windows-7-like-i-used-to-do-on-vista/